Cytokine Production by Peripheral Blood Mononuclear Cells and Metabolic Turnover of Bone During Pregnancy

We studied the dynamic turnover of bone by measuring metabolic markers in 6 healthy pregnant women, aged 23–28. Resorption markers, tartrate-resistant acid phosphatase and deoxypyridinoline, increased in the last trimester and after partrition decreased until puerperium day 30. The serum level of intact osteocalcin, a formation marker, exhibited a slight decrease during pregnancy and increased following childbirth. In the last trimester, the peripheral monocyte secreted much amount of interleukin (IL)-l and tumor necrosis factor (TNF)-α, potent stimulants of osteoclast, in parallel with the resorption markers. Estrogen has the bone sparing effect by inhibiting cytokine secretion in the bone microenvironment and peripheral mononuclear cell. Biomarker changes, however, disclosed uncoupling of bone with high resorption and low formation in the last trimester with a higher estrogen level than any other period of life, which might be mediated by a high amount of IL-1 and TNF-α through stimulating osteoclast activity.